The present invention relates to mining machines.
Conventional mining machines include a boom which projects forwardly from the machine and which carries a rotatable cutting head at its free end. The cutting head may be arranged to rotate about an axis parallel or perpendicular to the axis of the boom.
The efficiency with which the cutting head removes material from a working face is determind in part by the rate of rotation of the head. In soft materials, such as coal, the optimum cutting efficiency is obtained using a relatively high rate of rotation. In harder materials, for example some metal ores, a lower rate of rotation is more effective.
Some materials, for example iron ore, occur in deposits which contain two different types of material of different hardnesses. Since conventional mining machines having boom-mounted cutting heads can only be operated at a single cutting speed, the conventional machines cannot be used to work deposits of materials of differing hardnesses with optimum efficiency.
Accordingly, it is the primary object of the invention to provide a mining machine which can be used to excavate materials of different hardness at optimum efficiency.